Releasable tool attachment means for power trowels

ABSTRACT

A tool driver for a power trowel, the tool driver comprising a combination of a magnetic fastening arrangement and a friction based fastening arrangement for releasably holding an abrasive tool to the tool driver, wherein the magnetic fastening arrangement is configured symmetrically around a rotational center of the tool driver, wherein the friction based fastening arrangement is adapted to provide increased shear strength during abrasive operation of the tool, and wherein the magnetic fastening arrangement is adapted to provide increased pull strength during lifting of the tool driver.

TECHNICAL FIELD

The present disclosure relates to power trowels and to machines ingeneral for levelling and polishing concrete surfaces such as floors andthe like. There are disclosed means for attaching abrasive tools to oneor more power trowel tool drivers, in particular flexible abrasivetools. There are also disclosed adapters for attaching abrasive tools toexisting tool driver geometries.

BACKGROUND

Trowel polishing is a new trend in the construction industry. Trowelpolishing comprises use of abrasive tools, e.g., diamond tools, forsmoothing and polishing large concrete surfaces such as flooring and thelike. Similar equipment can also be used for polishing stone and marblesurfaces, although concrete is the most common.

A power trowel, also known as a “power float”, is a piece ofconstruction equipment used by construction companies and contractors toapply a smooth finish to concrete slabs. Power trowels differ in the waythey are controlled;

Walk-behind power trowels are used by an operator walking behind themachine.

Ride-on power trowels are used by an operator sitting on a seat upon themachinery, controlling the power trowel with control means.

A hand tool for the same task is often referred to as a concrete float.A float is used after the surface has been made level using a screed. Inaddition to removing surface imperfections, floating will compact theconcrete as preparation for further processing steps.

Power trowels use abrasive tools held by tool drivers for abradingsurfaces. The tool driver is rotatably attached to a motor which powersthe tool driver, and the tool is then attached to the tool driver forabrasive operation.

The abrasive tools used by the power trowel are replaced regularly by,e.g., tools having finer and finer grit size, and also as they are wornout. Thus, the tools are preferably arranged releasably held by the tooldriver of the power trowel to facilitate replacement. The tools need tobe held firmly enough such that they are not accidentally releasedduring abrasive operation due to shear forces acting on the tool driversand abrasive tools, but not too firmly since this would make toolreplacement inconvenient.

There is a need for abrasive tools and corresponding tool drivers whichfacilitate tool replacement while at the same time providing sufficientsupport for an efficient abrading operation.

SUMMARY

It is an object of the present disclosure to provide abrasive tools andtool drivers which facilitate tool replacement and at the same timeprovide for efficient and robust abrading operation without accidentaltool release.

This object is at least in part obtained by a tool driver for a grinder,power trowel, or other planetary grinding system. The tool drivercomprises a combination of a magnetic fastening arrangement and afriction based fastening arrangement for releasably holding an abrasivetool to the tool driver. The magnetic fastening arrangement isconfigured symmetrically around a rotational center of the tool driver.The friction based fastening arrangement is adapted to provide increasedshear strength during abrasive operation of the tool, while the magneticfastening arrangement is adapted to provide increased pull strengthduring lifting of the tool driver.

Thus, advantageously, both pull strength and shear strength are providedby the combination of fastening arrangements, while still allowing forconvenient tool replacement.

The disclosed techniques are particularly suitable for use withnon-rigid tools, i.e., tools comprising a flexible supporting elementfor holding an abrasive compound, such as fibrous pads and the like.

According to some aspects, the friction based fastening arrangementcomprises a tool driver surface with protrusions configured to engagewith a yielding surface material on the abrasive tool to provide theincreased shear strength.

The protrusions may, e.g., be pins molded in or otherwise attached tothe surface of the tool driver, thus providing a cost-efficient yetrobust friction based fastening arrangement that provides increasedfriction when engaging any type of yielding surface material, such as afibrous material or the like. The pins do not provide any significantpull strength but are complemented by the magnetic fasteningarrangement.

According to some other aspects, the friction based fasteningarrangement comprises a material with hooks for holding respective loopson the abrasive tool or the friction based fastening arrangementcomprises a material with loops for holding respective hooks on theabrasive tool.

Consequently, a hook and loop based fastening arrangement can also beused to provide increased friction. The hook side and the loop side canbe arranged on any of the tool driver or the tool, allowing forflexibility in manufacturing, which is an advantage.

According to aspects, the magnetic fastening arrangement comprises aplurality of magnets arranged symmetrically around a rotational centerof the tool driver.

Consequently, the tool can be rotated relative to the tool driver whilemaintaining pull strength. This simplifies tool replacement in that thetool need not be attached at any particular angle with respect to thetool driver.

According to other aspects, the magnetic fastening arrangement comprisesa metal element responsive to a magnetic force from the abrasive tool.

The magnetic fastening arrangement can be implemented with anycombination of metal elements and magnets, which is an advantage. Themetal element can, e.g., be a ring of metal having a diameter smallerthan a diameter of the tool driver. This saves cost since a smaller ringis used.

According to aspects, the tool driver comprises centering means forcentering the abrasive tool with respect to the rotational center of thetool driver.

The centering means further simplifies tool replacement, since no trialand error is required during tool alignment, which is an advantage.

According to aspects, the tool driver is furthermore arranged tointerface with a secondary tool driver.

This way the tool driver can function as an adapter to interface newtools with existing construction equipment, which is an advantage.

According to aspects, the magnetic fastening arrangement comprisesmagnets extending through the tool driver to engage with the abrasivetool on one side of the tool driver and to engage with the secondarytool driver on the other side of the tool driver.

The magnets thus have dual functions. On one side they act to provideincreased pull strength at the bond between tool driver and tool, and atthe other side they act to releasably attach the tool driver to thesecondary tool driver.

According to other aspects, the magnetic fastening arrangement comprisesmagnets on both sides of the tool driver, to engage with the abrasivetool on one side and to engage with the secondary tool driver on theother side of the tool driver.

According to aspects, the tool driver comprises protruding elementshaving shapes matched to corresponding recesses formed in the secondarytool driver. This way the tool driver interfaces with the secondary tooldriver to provide a robust grinding operation. The protruding elementshaving shapes matched to corresponding recesses formed in the secondarytool driver can be adapted to different secondary tool drivers, thusproviding an adaptation function with respect to a given secondary tooldriver.

The object is also obtained by an abrasive tool for a grinder, powertrowel, or other planetary grinding system. The abrasive tool comprisesa combination of a magnetic fastening arrangement and a friction basedfastening arrangement for being releasably held by a tool driver. Themagnetic fastening arrangement is configured symmetrically around arotational center of the tool. The friction based fastening arrangementis adapted to provide increased shear strength during abrasive operationof the tool, and wherein the magnetic fastening arrangement is adaptedto provide increased pull strength during lifting of the tool.

The friction based fastening arrangement may optionally be based onprotruding elements such as pins or a hook and loop based system.

The abrasive tool is configured for operation together with the tooldriver and is associated with the same advantages as the tool driver.

A loop side on the abrasive tool may according to some aspects beimplemented by a fibrous material, such as a felt-like cloth or similarfibrous material, which is a cost-effective way of producing the tool.This fibrous material is, according to aspects, a yielding and flexiblesupporting element for holding the abrasive compound. It is noted thatthis type of felt-like cloth or fibrous material is different from theknown Velcro loop-side that is a synthetic material comprising a specialtype of loops.

The disclosed tools are flexible and/or resilient, i.e., compressible tosome extent, and of sufficient strength. The fibrous tools made fromfelt, thick fabrics, and the like are possible to wash in water, andalso cost effective.

There are also disclosed herein construction equipment, grinders, powertrowels, and methods associated with the above-mentioned advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will now be described in more detail withreference to the appended drawings, where

FIGS. 1A, 1B and 2 schematically illustrate power trowels;

FIG. 3 shows an example tool configuration for a power trowel;

FIGS. 4A and 4B schematically illustrate a tool driver for a powertrowel;

FIGS. 5A and 5B schematically illustrate a tool for a power trowel tooldriver;

FIG. 6 illustrates a combination of tool and tool driver for powertrowels;

FIGS. 7A, 7B, 8A, 8B schematically illustrate centering means;

FIG. 9 schematically illustrates a tool driver for a power trowel;

FIG. 10 schematically illustrates a tool for a tool driver;

FIG. 11 shows a collection of example magnet shapes;

FIG. 12 schematically illustrates a tool driver for a power trowel;

FIG. 13 schematically illustrates a tool for a power trowel tool driver;

FIG. 14 is a flow chart illustrating methods;

FIGS. 15A and 15B schematically illustrate a tool for a power trowel;and

FIGS. 16A, 16B, 17A-C, 18, and 19A-B schematically illustrate tooldrivers.

DETAILED DESCRIPTION

Aspects of the present disclosure will now be described more fullyhereinafter with reference to the accompanying drawings. The differentdevices and methods disclosed herein can, however, be realized in manydifferent forms and should not be construed as being limited to theaspects set forth herein. Like numbers in the drawings refer to likeelements throughout.

The terminology used herein is for describing aspects of the disclosureonly and is not intended to limit the invention. As used herein, thesingular forms “a”, “an” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise.

Herein, a rotational center is a point on an object which stays fixed asthe object is rotated. It is appreciated that objects which are notdesigned to rotate during operation still have rotational centers. Forinstance, the rotational center of any disc-shaped object coincides withthe center of the disc. The rotational center of a square object alsocoincides with the center of the square object.

FIGS. 1A, 1B and 2 schematically illustrate power trowels 100, 200 forabrading, levelling and/or polishing surfaces 140, such as concretesurfaces. The power trowels 100 are walk-behind power trowels while thepower trowel 200 is a ride-on power trowel.

A walk-behind power trowel 100 comprises a handle 110 which the operatoruses to guide the trowel. There is a power source 120, a combustionengine or electrical motor, which powers the trowel 130.

The ride-on power trowel 200 has a seat with control means 210 where anoperator sits and controls the power trowel 200. There is again a powersource 220 which powers the trowel 230.

Power trowels are generally known and will not be discussed in moredetail here.

The abrasive tools disclosed herein comprise an abrasive component orcompound arranged on a side of the abrasive tool opposite to the sidewhich attaches to the tool driver. Thus, an abrasive operation isperformed when the tool is rotated or otherwise brought innon-stationary contact with a material to be abraded.

The abrasive component may be realized in many different ways; forinstance, abrasive coins may be bonded to a ring, such as a plasticring, which is glued to the tool. An abrasive compound can be sprayedonto the tool and bonded thereon by a resin. The pad itself may also beimpregnated by a compound comprising, e.g., diamond particles or thelike.

Herein, a tool driver may also be referred to as a tool holder. It isappreciated that a tool driver need not necessarily be arranged torotate about its own center. Rather, a tool driver may be fixedlyattached to an arm which is rotating around some other center ofrotation.

Herein, a tool driver can be directly attached to the grinding machine,as illustrated in FIGS. 7A and 7B, or it can be an adapter used tointerface between a given abrasive tool and a secondary tool driverattached to the grinding machine, as illustrated in FIGS. 16A and 16B.

The disclosed techniques can be used for abrasive operation by a widevariety of different tools and construction equipment, such as singledisc grinders, passive planetary systems, and active planetary systems.The disclosed tools and tool drivers are especially suited or use withpower trowels but can also be used with other surfacing machines such asfloor cleaning machines and floor polishing machines.

FIG. 3 shows an example tool configuration for a power trowel. A powertrowel may comprise one or more such tool configurations, e.g., 1, 2, oreven 4. The trowels 130, 230 comprise tool drivers 300 to which abrasivetools can be releasably held. Power trowels commonly comprise between8-12 abrasive tools. The abrasive tools are often disc-shaped with adiameter of 14″. However, tool diameters from 7-25 inches may be usedwith the disclosed techniques.

Known tool drivers comprise hook-and-loop systems for releasably holdingthe abrasive tool.

Hook-and-loop fasteners, hook-and-pile fasteners or touch fasteners(often referred to by the genericized trademark Velcro), consist of twocomponents: typically, two fabric strips or, alternatively, round “dots”or squares which are attached (glued, riveted, sewn or otherwiseadhered) to the opposing surfaces to be fastened. The first componentfeatures tiny hooks, the second features smaller loops. When the two arepressed together the hooks catch in the loops and the two pieces fastenor bind temporarily. When separated, by pulling or peeling the twosurfaces apart, the strips make a distinctive “ripping” sound.

Herein, a friction based fastening arrangement is an arrangement whichprovides increased friction between two surfaces in order to betterresist a shear force acting on the surfaces. Examples of friction basedfastening arrangements include arrangements where one surface comprisesprotrusions or pins 1605 and the other side is configured with ayielding material such as fibrous material which the protrusions maypuncture, enter or be received by in some way. When the pins orprotrusions extend into the yielding material, increased friction isobtained. Thus, the feature of having protrusions configured to engagewith a yielding surface material is to be interpreted broadly. Oneexample is molded pins extending from one surface to puncture orotherwise enter another surface such as a fibrous material surface or arubber surface.

It is appreciated that the tool drivers illustrated in FIGS. 4A, 4B, 7Aand 7B can be used with any type of friction-based fastening system,including hook-and-loop based system and protrusion based systems.

It is appreciated that the tool drivers illustrated in FIGS. 16A and 16Bcan be used with any type of friction-based fastening system, includinghook-and-loop based system and protrusion based systems.

Another example of a friction based fastening arrangement is the hookand loop based fastening arrangement discussed above; Herein, a hook andloop based fastening arrangement is any arrangement which uses the hookand loop principle to releasably hold one element to another element. Itis appreciated that hook and loop based fastening arrangements comprisearrangements where hooks are arranged on one element and loops arearranged on the other element, regardless of which element is which.Hook and loop based fastening arrangements also comprise configurationswhere combinations of hooks and loops are arranged on both elements.

Herein, hook and loop based as well as friction based fasteningarrangements also comprise arrangements where the loop side or yieldingsurface material side comprises a fibrous material, such as a cloth orfelt-like material. It is appreciated that most fibrous materials areyielding and therefore configured to receive pins or protrusions andattach to some extent to a hook side of a hook and loop based fasteningarrangement, since the hooks catch on to the fibers in the fibrousmaterial. Such fibrous materials may optionally be used as supportingelement for the abrasive compound that performs the abrasive operationof the abrasive tool. Thus, a flexible or at least partly non-rigid toolis provided.

The loop side may also comprise other types of flexible materials, e.g.,foam-based materials and rubber.

It has been realized that fastening means based only on hook and looparrangements provide high resistance to the shear forces exerted ontools during abrasive operation, which is an advantage. However, hookand loop arrangements do not provide very large resistance to the pullforces which are exerted on tools as the trowel is lifted from thesurface during tool replacement, especially if the loop-side isconstituted by a fibrous material instead of a conventional ‘Velcro’loop-side. Such fibrous materials often provide reduced pull strengthcompared to conventional Velcro-like loop side materials.

The same conclusion holds for a friction based fastening arrangementbased on protrusions. This type of fastening arrangement provides shearforce resistance but very little pull force resistance.

A magnetic fastening arrangement, as referred to herein, is anyarrangement which is able to releasably hold one element to anotherelement by means of a magnetic force exerted by one or both elementsonto the other. Thus, magnetic fastening means comprises arrangementswhere one element is configured with electromagnetic or permanentmagnets while the other element is configured with metal responsive to amagnetic force, such as iron, nickel, cobalt, or certain rare earthmetal alloys such as neodymium. Magnetic fastening means also comprisesarrangements where both elements are configured with magnets ofdifferent polarity, or combinations of magnetic metals and magnets.

It has been realized that fastening means based only on magneticarrangements are too weak for use with power trowels when it comes toshear force resistance. This means that, during abrasive operation, thetool may slide off the tool driver, which causes interruption of theabrasive operation.

However, magnetic fastening means do provide the sought resistance topull forces which are exerted on the tool as the trowel is lifted fromthe surface during tool replacement.

Also, when magnetic fastening arrangements are used to complement thefriction based fastening arrangement, reduced pull strength is neededfrom the friction based fastening arrangement. Thus, in combination withthe magnets, a simple friction based fastening arrangement based onprotruding pins entering a fibrous material may be sufficient for manygrinding applications.

The tools and tool drivers disclosed herein comprise a combination ofmagnetic fastening means and friction based fastening means, which is anadvantage since the combination of fastening means facilitate toolreplacement and at the same time provide for efficient and robustabrading operation. The combination of the friction, and magnetic systemensures that the tool is attached with a strong shear resistance andpull-apart strength.

There are disclosed herein combinations of magnetic fastening means andhook-and-loop based fastening means, as well as combinations of magneticfastening means and protrusion based fastening means. Any of these typesare usable with adapter type tool drivers as illustrated in FIGS. 16Aand 16B.

The combination of magnetic fastening means and friction based fasteningmeans is especially suited for flexible tools where a fibrous yieldingmaterial, such as felt or the like, is used to support the abrasivecompound.

As mentioned above, tools and corresponding tool drivers having adiameter between 7 inches and 25 inches are suitable for the disclosedtechniques.

A preferred size of the tools and tool drivers disclosed herein is adiameter of 11 inches.

Another preferred size of the tools and tool drivers disclosed herein isa diameter of 14 inches.

It is appreciated that the disclosed techniques are applicable also forlarger tools and corresponding tool drivers of up to 48 inches.

There are disclosed herein arrangements 130, 230 for abrasive operationby a grinder such as a power trowel 100, 200 comprising at least one,and preferably a plurality of, tool drivers and a corresponding numberof abrasive tools which facilitate tool replacement and at the same timeprovide for efficient and robust abrading operation.

There are also disclosed power trowels 100, 200 comprising one or moreabrasive tools and/or tool drivers as discussed herein.

FIGS. 4A and 4B schematically illustrate a tool driver 400 for a powertrowel such as the power trowels 100, 200 discussed above. At least onemagnet 410, preferably a plurality of magnets, are arranged on the tooldriver symmetrically 415 around a rotational center 416 of the tooldriver. Here, a hole is shown in the center. It is appreciated that thishole 430 is optional, i.e., not necessary for the overall function asdescribed herein.

The disclosed tool driver and tool combinations are suitable for anyplanetary grinding system using rotating tools for grinding or polishingsurfaces.

There is also a protrusion or hook component in a friction basedfastening system 420 arranged on the tool driver. Here the protrusionsor hooks are shown covering the whole tool driver 400 except for thehole 430, but the hooks can just as well cover only a part of the tooldriver.

Consequently, the tool driver 400 shown in FIGS. 4A and 4B comprises acombination of a magnetic fastening arrangement 410 and a friction basedfastening arrangement 420 for releasably holding an abrasive tool to thetool driver. The magnetic fastening arrangement 410 is configuredsymmetrically 415 around a rotational center 416 of the tool driver. Itis understood that the magnets are fixedly attached to the tool driver.

It is preferred that the hooks cover a symmetric area centered aroundthe rotation center 416 of the tool driver 400, such that the tool neednot be aligned with the tool driver angularly.

FIG. 4B shows a side view along section A-A of the tool driver 400. Thecombination of magnetic fastening arrangement 410 and friction basedsystem 420 is shown. The tool driver also comprises a support structure440 for attaching to the power source and for providing structuralintegrity to the tool driver.

As discussed above, the friction based fastening arrangement is adaptedto provide increased shear strength during abrasive operation of thetool, while the magnetic fastening arrangement is adapted to provideincreased pull strength during lifting of the tool driver. Thiscombination is advantageous in that it facilitates tool replacement atthe same time as it provides for a robust abrasive operation withoutinterruptions due to tool loss. It was previously thought that only ahook and loop-based system, was sufficient for this application.

The tool driver 400 comprises the protrusion side or hook side of afriction based fastening arrangement, which is a preferredconfiguration. It is however, appreciated that the tool driver can alsocomprise the loop side or yielding material side.

According to some aspects, the friction based fastening arrangement is ahook and loop based fastening arrangement on the tool driver thatcomprises hooks for holding respective loops on the abrasive tool.According to some other aspects, the hook and loop based fasteningarrangement on the tool driver comprises loops for holding respectivehooks on the abrasive tool. An example of such loops is a fibrous pad.

A friction based fastening arrangement based on pins or otherprotrusions extending into a yielding surface material instead comprisesa surface with protrusions configured to engage with a yielding surfacematerial on the abrasive tool to provide the increased shear strength.

As mentioned above, the magnetic fastening arrangement may comprise aplurality of magnets 410 arranged symmetrically 415 around a rotationalcenter of the tool driver.

According to other aspects, the magnetic fastening arrangement comprisesa metal element which is responsive to a magnetic force from theabrasive tool.

The metal element is thus arranged to be releasably held by one or moremagnets.

FIGS. 5A and 5B schematically illustrate a tool 500 for a tool driversuch as that illustrated in FIG. 5A.

FIG. 5A shows an abrasive tool 500 for a power trowel 100, 200. Theabrasive tool comprises a combination of a magnetic fasteningarrangement 510 and a friction based fastening arrangement 520 for beingreleasably held by a tool driver such as the tool driver 400 discussedabove. The magnetic fastening arrangement 510 is configuredsymmetrically around a rotational center 516 of the tool.

FIG. 5B shows a side view of the tool 500 along cross section B-B. Theabrasive coating 550 is shown in FIG. 5B, it is this coating thatabrades the material which is to be levelled or polished. The tool alsocomprises a support structure 540 which provides mechanical integrity.The combination of friction-based fastening means 520 and magneticfastening means 510 can also be seen in FIG. 5B. Again, advantageously,the friction based fastening arrangement 520 is adapted to provideincreased shear strength during abrasive operation of the tool, and themagnetic fastening arrangement 510 is adapted to provide increased pullstrength during lifting of the tool.

According to aspects, the friction based fastening arrangement is a hookand loop system where the tool comprises hooks for holding respectiveloops on the corresponding tool driver.

According to other aspects, the friction based fastening arrangement onthe tool comprises loops, e.g., a fibrous pad, for holding respectivehooks on the tool driver.

According to some aspects, the abrasive component on the tool issupported at least partly by a flexible supporting element, such as thefibrous pad. Thus, the tool is not necessarily mounted on a rigidsupporting element but may flex and bend somewhat to followirregularities in the material to be abraded.

It is appreciated that the loop side on the abrasive tool may accordingto some aspects be implemented by a fibrous material, such as afelt-like cloth or similar fibrous material, which is a cost-effectiveway of producing the tool. It is noted that this type of felt-like clothor fibrous material is a yielding material different from the knownVelcro loop-side that is a synthetic material comprising a special typeof loops. Also, the felt-like cloth or fibrous material constitutes aflexible carrier for an abrasive material, providing a flexible toolhaving a yielding surface material suitable for receiving pins orprotrusions of a friction based fastening arrangement.

The configuration of magnetic fastening means in FIG. 5B is a metal bandarranged symmetrically around the rotational center 516. It is however,appreciated that magnets can be arranged also on the tool, albeit with adifferent polarity compared to the corresponding tool driver.

Thus, according to aspects, the magnetic fastening arrangement comprisesa plurality of magnets 410 arranged symmetrically around a rotationalcenter of the abrasive tool.

According to other aspects, the magnetic fastening arrangement comprisesa metal element responsive to a magnetic force from the tool driver.

A circularly shaped or otherwise rotationally symmetric shaped magnetictape can optionally be attached to the fibrous pad of the tool toprovide magnetic attachment force.

FIG. 6 shows a tool and tool driver combination 600. It is seen that themagnets 410 align with the metal band 510. Since both magnets and metalband are arranged symmetrically around the rotational center of the tooland driver, respectively, there is always overlap between magnets andmetal band, regardless of in which angle the tool is turned relative tothe driver, which is an advantage since it simplifies tool replacement.It is also noted that the elements of the friction based fastening meansoverlap and thus engage releasably with each other.

FIG. 6 also illustrates the force direction S of the shear forces whichact on the tool during abrasive operation, and the gravitational pullforces P which act on the tool when the trowel is lifted from thesurface during tool replacement.

FIGS. 7A and 7B schematically illustrate centering means.

A potential issue relates to a scenario when the tool 800 is notattached centered with respect to the tool driver 800. If the toolcenter does not align with the tool driver center, then fastening meansmay not be as effective. For instance, magnets 410 may not contact themetal band 510 with a reduced pull force resistance as consequence.

To alleviate this issue, the tool driver 700 comprises centering means710 for centering the abrasive tool with respect to the rotationalcenter 416 of the tool driver.

The centering means 710 may comprise centering elements arranged aroundthe circumference of the tool driver as shown in FIG. 7A. The centeringelements only allow the tool to contact the tool driver if therotational centers are aligned, otherwise the tool will not attach. Thisis an advantage since it simplifies tool replacement and provides for amore robust abrasive operation with a reduction in involuntary toolrelease.

FIG. 7B shows a side view of the tool driver 700 when receiving a tool500. The tool 500 will only attach to the driver if it passes thecentering means 710, which is an advantage.

Thus, according to aspects, the tools disclosed herein may comprisecentering means 810 for centering the abrasive tool with respect to arotational center 416 of the tool driver.

FIGS. 8A and 8B schematically illustrate other example centering means.Here, a tap 810 is arranged protruding from the tool 800. The tap isconfigured to be received in a corresponding hole 430 in the tool driver400.

FIG. 8B illustrates the tool 800 being attached to a tool driver 400.Only when the centering means enters the hole 430 can the tool 800attach to the driver 400.

The tap arrangements and centering element arrangements can be used incombination for additional centering robustness.

It is appreciated that the magnetic fastening means discussed above arealso providing a centering function, since the magnets will exert amagnetic force only when aligned with the corresponding magneticfastening element on the tool or tool driver. Thus, a centering actionby the magnets follow from the rotationally symmetric configuration ofthe magnetic fastening means.

FIG. 9 schematically illustrates a tool driver 900 for a power trowel.This tool driver comprises the loop or yielding surface component 420 ofthe friction based fastening means. It is this appreciated that thefriction based fastening means can be arranged in different ways whilemaintaining the technical effects discussed herein.

The tool driver 900 also comprises a metal band 520 instead of magnets,this illustrates that magnets and metal band can be exchanged orswitched between tool and tool driver while maintaining the technicaleffects discussed herein.

FIG. 10 schematically illustrates a tool 1000 for a tool driver. Thistool comprises the hook element 520 of a hook and loop based fasteningarrangement, and also the magnets 410. The tool 1000 thereforecorresponds to and can be releasably held by the tool driver 900. Thetool 1000 may also comprise protrusions arranged to engage with ayielding surface material of the tool driver 900.

FIG. 11 shows a collection of example magnet shapes 1110, 1120, 1130,1140. It is appreciated that magnets can have varying shape and can alsobe applied as a band 1140 around the rotational center of any of thetool or the tool driver.

FIG. 12 schematically illustrates a tool driver 1200 for a power trowel.This tool driver has a rectangular shape which may be advantageous insome polishing scenarios.

FIG. 13 schematically illustrates a tool 1300 corresponding to the tooldriver 1200.

FIG. 14 is a flow chart illustrating methods. There is shown a method ofattaching a tool 500, 800, 1000, 1300 to a tool driver 400, 700, 900,1200 for a power trowel 100, 200. The method comprises configuring S1 acombination of a magnetic fastening arrangement 410, 510 and a frictionbased fastening arrangement 420, 520 for releasably holding an abrasivetool 500, 800, 1000, 1300 to the tool driver, wherein the magneticfastening arrangement 410, 510 is configured symmetrically 415 around arotational center 416 of the tool driver. The method also comprisesreleasably holding S2 the tool by the tool driver.

FIGS. 15A and 15B schematically illustrate a tool for a power trowel.The tool is, according to aspects, a pad assembly 10 such as thatexemplified in FIGS. 15A-15B. Pad assembly 10 may be used for grindingor polishing composite surfaces, such as concrete. Pad assembly 10includes a wear-resistant base pad 12, which may be a porous, fibrous,flexible, and deformable material, including natural and/or artificialfibres. Base pad 12 is generally circular, having a diameter and athickness. Of course, base pad 12 could be made in other sizes.

A reinforcement ring or layer 14 is secured to one side of base pad 12,such as by adhesive. The reinforcement ring 14 is generally annularhaving a central opening 18 with a diameter (for example, approximately8 inches). Reinforcement ring 14 may be a rigid rubber or plastic havinga thickness greater than zero and up to 0.125 inch. Reinforcement ringor layer 14 reinforces and adds some stiffness and toughness to theouter portion of pad 12, however, ring or layer 14 allows someflexibility to pad assembly 10 so it can flex with and follow any floorimperfections thereby producing uniform floor contact for polishing orgrinding.

A circular internal edge 17 of reinforcement ring 14 defines a centralopening or hole 18 which exposes a central surface 20 of base pad 12.Central surface 20 of base pad 12 may according to an example beimpregnated with diamond particles or other abrasive materials. Centralsurface 20 of the base pad 12 may also be painted with a colourindicating a quality of the pad assembly 10, such as the coarseness.Base pad 12 and ring 14 preferably have circular peripheral surfaces 19and 21, respectively.

In the example of FIGS. 15A and 15B, a plurality of abrasive tools orfloor-contacting disks 16 are secured to the outer surface of thereinforcement ring 14. In the example shown, abrasive tools 16 areapproximately 2-inch disks of diamond particles in a polymeric resinmatrix. In the example shown, six such abrasive tools or disks 16 aresecured about the circumference of reinforcement ring 14. Differentsizes and different compositions of abrasive tools or disks 16 could beused. Tools or disks 16 are adhesively bonded to ring 14.

FIG. 15B shows base pad 12. Again, different base pads 12 could be used,but the example shown is a wear-resistant base pad 12 having a diameterof approximately 14 inches and a thickness of approximately one inch. Ametal ring here constitutes the magnetic fastening means. The metal ringis glued to the upper surface of the tool. The ring has an outerdiameter smaller than the outer diameter of the reinforcement ring 14.

To summarize, FIGS. 15A and 15B exemplify an abrasive tool 1500comprising;

a fibrous pad 12 including an upper surface, a floor-facing lowersurface and a peripheral surface;a reinforcement layer 14 attached to the bottom surface of the pad, thereinforcement layer including an internal edge 17 defining a holetherethrough; abrasive disks 16 attached to a floor-facing surface ofthe reinforcement layer;a central area 20 of the pad being exposed through the hole of thereinforcement layer such that a linear dimension of the central areawithin the hole is greater than a linear dimension of one side of thereinforcement layer between the hole and a periphery thereof; anda magnetic ring 22 arranged on the upper surface which constitutes themagnetic fastening arrangement, wherein the magnetic ring has an outerdiameter smaller than an outer diameter of the reinforcement layer 14.

FIG. 16A schematically illustrates a front side of a tool driver 1600configured to attach to an abrasive tool, such as the tool 1500 shown inFIGS. 15A and 15B. FIG. 16B schematically illustrates a back side of thetool driver 1600 configured to attach to a secondary tool driver 2. Thesecondary tool driver will be discussed in connection to FIG. 18 below.

The tool driver 1600 is arranged to interface with the secondary tooldriver 2, thereby assuming the function of an adapter. By using the tooldriver 1600, a tool such as the tool 1500 shown in FIGS. 15A and 15B canbe used with existing grinding machines.

In the example of FIGS. 16A and 16B, the tool driver 1600 has a magneticfastening arrangement which comprises front-side magnets 410 and backside magnets 410′ arranged distributed on respective circles.

According to some aspects (not shown in FIG. 16A or 16B), the front sidemagnets 410 extend through the tool driver, from the front side to theback side to engage with the abrasive tool on the front side of the tooldriver and to engage with the secondary tool driver 2 on the back sideof the tool driver. In this case the back side magnets 410′ are notnecessary.

According to some aspects, the tool driver 1600 comprises protrudingelements 1610 having shapes matched to corresponding recesses 4, orfixing means 4, formed in the secondary tool driver 2.

The tool driver 1600 shown in FIGS. 16A and 16B is configured with acombination of magnetic fastening arrangement providing pull strength,while the protruding elements 1605, or pins, is a friction basedfastening arrangement adapted to provide increased shear strength duringabrasive operation of the tool. The magnetic fastening arrangement 410,410′ is configured symmetrically around a rotational center of the tooldriver.

The tool driver 1600 may, according to some aspects, also be configuredwith the type of hook-and-loop based fastening arrangement discussedabove.

According to some aspects, one or more notches 1620 are formed in therim 1630 of the tool driver. The notches or cut-out portions allow afinger, hand, or tool to get better purchase when removing the tooldriver from, e.g., a secondary tool driver 2. For instance, a servicetechnician or operator of a grinding machine can get purchase on thetool driver by inserting a finger into the notch 1620.

FIGS. 17A-17C show additional views of the tool driver 1600. Noteespecially the protrusions or pins 1605 and the recesses 1620. Note alsothat the pins 1605 are shown as an example, a hook-and-loop basedfastening arrangement can also be used instead of, or in combinationwith, the pins 1605.

FIG. 18 schematically illustrates an example secondary tool driver 2.The secondary tool driver 2 has a front side and a back side, whichfront side is facing the ground during the grinding process. Thesecondary tool driver 2 further has a circular opening 6 in the centerto guide the disc when attaching it to a grinding machine. A pluralityof screw holes 5 are situated around the secondary tool driver 2 to beused for tightening of the secondary tool driver 2 when put into placein a grinding machine. Grooves 7 are distributed radially outwards fromthe center of the tool driver 2 and are evenly distributed around thecircumference of the disc. Each groove 7 is of a conical shape taperingradially outwards from the center of the disc. Two carrier plates willbe attached to a first 3 and a second 4 fixing means in such a way thatabrasive elements of respective carrier plate will overlap radially.This is accomplished in that the grooves of first 3 and second 4 fixingmeans are distributed so that the innermost end 3 b of the first fixingmeans 3 and the outermost end 4 a of the second fixing means 4 partlyoverlap each other in the radial direction. In a preferred way, theinnermost second fixing means 4 are disposed circumferentially inbetween two adjacent outermost first fixing means 3 in such a way thatthe first and the second fixing means will not extend along the sameradial line

In FIG. 18, the grooves 7 of the innermost second fixing means 4 areplaced in such a way that the innermost end 4 b of each fixing meanopens up toward the opening at the center of the disc 6. In the shownexample of FIG. 18, the disc 2 comprises six first fixing means 3 andsix second fixing means 4. However, it is clear to a person skilled inthe art that one disc could comprise anywhere from two or more fixingmeans sharing the same predetermined distance to the center of the disc.Moreover, a secondary tool driver according to the present disclosurecould comprise more than two fixing means, preferably distributed evenlyaround an secondary tool driver to balance the disc, and each having acertain predetermined distance to the center of a disc that is differentfrom the distance of any other fixing means on the same disc. Thissecondary tool driver 2 and its use was discussed in detail in EP 2 337653 B1, where it is referred to as an abrasive disc. It will thereforenot be described in more detail herein.

FIGS. 19A and 19B illustrate another example tool driver 1900. This tooldriver is similar to the tool driver 1600 shown in FIGS. 16 and 17, butinstead uses wings 1910 having shapes matched to a secondary tool drivershape. The wings 1910 are protruding elements having shapes matched tocorresponding recesses formed in the secondary tool driver.

Similar to the example tool driver in FIGS. 16A-B and FIG. 17A-C, one ormore notches 1620 are formed in rim portions of the wings 1910. Thenotches or cut-out portions allow a finger, hand, or tool to get betterpurchase when removing the tool driver from, e.g., a secondary tooldriver 2.

The tool driver 1900 shown in FIGS. 19A and 19B is configured with acombination of magnetic fastening arrangement providing pull strength,while the protruding elements 1605, or pins, is a friction basedfastening arrangement adapted to provide increased shear strength duringabrasive operation of the tool. The magnetic fastening arrangement 410,410′ is configured symmetrically around a rotational center of the tooldriver.

1. A tool driver for a power trowel, the tool driver comprising acombination of a magnetic fastening arrangement and a friction basedfastening arrangement for releasably holding an abrasive tool to thetool driver, wherein the magnetic fastening arrangement is configuredsymmetrically around a rotational center of the tool driver, wherein thefriction based fastening arrangement is adapted to provide increasedshear strength during abrasive operation of the tool, and wherein themagnetic fastening arrangement is adapted to provide increased pullstrength during lifting of the tool driver.
 2. The tool driver accordingto claim 1, wherein the friction based fastening arrangement comprises atool driver surface with protrusions configured to engage with ayielding surface material on the abrasive tool to provide the increasedshear strength.
 3. The tool driver according to claim 1, wherein thefriction based fastening arrangement comprises a material with hooks forholding respective loops on the abrasive tool or wherein the frictionbased fastening arrangement comprises a material with loops for holdingrespective hooks on the abrasive tool.
 4. The tool driver according toclaim 2, wherein the yielding surface material or the material withloops is a felt-like cloth, a fibrous material, a foam, rubber, and/or anon-synthetic material.
 5. The tool driver according to claim 1, whereinthe magnetic fastening arrangement comprises a plurality of magnetsarranged symmetrically around a rotational center of the tool driver. 6.The tool driver according to claim 1, wherein the magnetic fasteningarrangement comprises a metal element responsive to a magnetic forcefrom the abrasive tool.
 7. The tool driver according to claim 1, whereinthe tool driver comprises centering means for centering the abrasivetool with respect to the rotational center of the tool driver.
 8. Thetool driver according to claim 1, wherein the tool driver has a diameterbetween 7 and 25 inches.
 9. The tool driver according to claim 1,wherein the tool driver is arranged to interface with a secondary tooldriver.
 10. The tool driver according to claim 9, wherein the magneticfastening arrangement comprises magnets extending through the tooldriver to engage with the abrasive tool on one side of the tool driverand to engage with the secondary tool driver on the other side of thetool driver.
 11. The tool driver according to claim 9, comprisingprotruding elements having shapes matched to corresponding recessesformed in the secondary tool driver.
 12. The tool driver according toclaim 9, comprising one or more notches formed in the rim of the tooldriver, to allow a better grip by a hand removing the tool driver fromthe secondary tool driver.
 13. An abrasive tool for a power trowel, theabrasive tool comprising a combination of a magnetic fasteningarrangement and a friction based fastening arrangement for beingreleasably held by a tool driver on a first side of the abrasive tool,wherein the magnetic fastening arrangement is configured symmetricallyaround a rotational center of the tool, wherein the friction basedfastening arrangement is adapted to provide increased shear strengthduring abrasive operation of the tool, and wherein the magneticfastening arrangement is adapted to provide increased pull strengthduring lifting of the tool.
 14. The abrasive tool according to claim 13,wherein the friction based fastening arrangement comprises a yieldingsurface material configured to engage with protrusions on arranged onthe tool driver surface to provide the increased shear strength.
 15. Theabrasive tool according to claim 13, wherein the friction basedfastening arrangement comprises a surface material with hooks forholding respective loops on the tool driver or wherein the frictionbased fastening arrangement comprises a surface material with loops forholding respective hooks on the tool driver. 16-20. (canceled)
 21. Theabrasive tool according to claim 13, comprising an abrasive component orcompound arranged on a second side of the abrasive tool opposite to thefirst side.
 22. The abrasive tool according to claim 21, wherein theabrasive component is supported at least partly by a flexible supportingelement.
 23. The abrasive tool according to claim 13, wherein themagnetic fastening arrangement comprises a metal ring having a diametersmaller than a diameter of the tool.
 24. The abrasive tool according toclaim 13, comprising; a fibrous pad including an upper surface, afloor-facing lower surface and a peripheral surface; a reinforcementlayer attached to the bottom surface of the pad, the reinforcement layerincluding an internal edge defining a hole therethrough; abrasive disksattached to a floor-facing surface of the reinforcement layer; a centralarea of the pad being exposed through the hole of the reinforcementlayer such that a linear dimension of the central area within the holeis greater than a linear dimension of one side of the reinforcementlayer between the hole and a periphery thereof; and where a magneticring arranged on the upper surface constitutes the magnetic fasteningarrangement, wherein the magnetic ring has an outer diameter smallerthan an outer diameter of the reinforcement layer.
 25. (canceled) 26.(canceled)
 27. A method of attaching an abrasive tool to a tool driverfor a power trowel, comprising; configuring a combination of a magneticfastening arrangement and a friction based fastening arrangement forreleasably holding an abrasive tool to the tool driver, wherein themagnetic fastening arrangement is configured symmetrically around arotational center of the tool driver; and releasably holding the tool bythe tool driver.